This invention relates generally to an image forming apparatus using a xerography system and an image-carrier cartridge device which is employed in the same. In one aspect, this invention relates to an image-carrier cartridge device having protective covers for preventing an abnormal condition which comes from light reaching a surface of an image carrier (a photoreceptor), and mechanical contact, and especially to an art for preventing frictional charge which occurs on the cover surfaces, and abnormal discharge from the image carrier caused thereby. Further, the invention relates to the image forming apparatus which prevents damages to a photoreceptor caused by foreign matter (e.g., paper particles) gathering and solidifying in foam cells, and prevents filming by rubbing the image-carrier cartridge device. Furthermore, the invention relates to the image forming apparatus which flicks a developer deposited on a conductive brush, and prevents bristles of the brush from bending.
Conventionally, an image carrier such as the photoreceptor which is employed in an image forming apparatus using a xerography system (hereinafter the image carrier is referred to as the photoreceptor), has been formed in a cartridge unit, and loaded into the image forming apparatus for use. This cartridge unit is equipped with protective covers (shutters) which close before loading in the image forming apparatus in order to prevent the abnormal condition caused by light reaching the surface of the photoreceptor or mechanical contact, and open at the time of loading.
However, if the protective covers of the above-mentioned cartridge unit have a low stiffness, the surface of the photoreceptor may be damaged by contact with the protective covers during handling. Also, the protective covers are touched by workers in an assembly line, and rubbed by packing materials during shipment, so that the surfaces of the protective covers, which are made of resin materials, may be charged with frictional electricity. If the frictional charging settles dust on the surfaces (both of inner and outer sides) of the protective covers, the dust will be transferred onto the surface of the photoreceptor, which will bring on the adverse effect.
Moreover, when the cartridge unit is loaded into the image forming apparatus in a state wherein the protective covers are charged with frictional electricity on the surface thereof, and when the protective covers are opened, sparking is prone to occur between the protective covers and the photoreceptor. In such a case, the sparking damages the photoreceptor (photoreceptive layer), thereby generating pinholes. This causes various kinds of image noise (such as so-called black line).
An action of generating the above-mentioned phenomenon is illustrated in FIG. 7. When the protective covers facing the photoreceptor are opened in a state of being charged with frictional electricity, the sparking between the protective covers and the photoreceptor makes pinholes on the photoreceptor. The electricity is charged onto the damaged photoreceptor by a pre-charge film, abnormal discharge occurs at points of the pinholes, and toner fuses and develops as a result of the discharging heat. If an image on the photoreceptor is developed by a developing roller in this state, it will not develop properly.
Further, there has been proposed an image forming apparatus of the cleaner-less type in which the developer remaining on the photoreceptor surface is not removed by a cleaner. In this type of the image forming apparatus, the electrostatic latent image is formed by exposing the surface of the photoreceptor which is charged by a conductive brush. Then, the latent image is revealed with the developer, and transferred onto the paper. After that, a developing-cleaning means collects the developer which remains on the photoreceptor without being transferred onto the paper in the latest printing operation.
If various sorts of papers are used for forming the images, wherein foreign matter such as paper particles is deposited on the photoreceptor, then these foreign matter is also gathered together with the developer. Using the developer which contains the foreign matter, causes degradation in the images. To deal with the above-mentioned problem, an image forming apparatus has been proposed wherein an elastic member, which is a foam body having a plurality of foam cells of 0.1-1.0 mm in diameter, is pushed onto the photoreceptor in order to remove the foreign matter, such as the paper particles deposited on the photoreceptor, and let the developer remaining on the photoreceptor pass through.
However, in the above-mentioned image forming apparatus, the foreign matter such as the paper particles deposited on the photoreceptor gathers and solidifies in the foam cells, and the solidified matter may damage the photoreceptor. Further, in the image forming apparatus of the cleaner-less type, the surface of the photoreceptor may be filmed (this phenomenon is hereinafter referred to as filming). The filming should be avoided since it causes various problems such as nonuniformity in charging, exposing and developing.
Moreover, in the image forming apparatus using the conductive brush for charging the photoreceptor surface with electricity, toner remaining on the photoreceptor may be deposited on the photoconductive brush. The deposited toner makes the brush dirty, which may bring on degradation in charging, and bring on image noise or filming. Accordingly, a flick member is provided to touch the brush in order to remove the deposited toner.
However, if the flick member always touches with the brush, fiber bristles planted in the conductive brush are bent. The bent bristles cause degradation in charging and image quality.